TRANSIENT DEAFNESS ACCOMPANIES AUDITORY DEVELOPMENT DURING METAMORPHOSIS FROM TADPOLE TO FROG

During metamorphosis, ranid frogs shift from a purely aquatic to a par tly terrestrial lifestyle. The central auditory system undergoes funct ional and neuroanatomical reorganization in parallel with the developm ent of new sound conduction pathways adapted for the detection of airb orne sounds. Neural responses to sounds can be recorded from the audit ory midbrain of tadpoles shortly after hatching, with higher rates of synchronous neural activity and lower sharpness of tuning than observe d in postmetamorphic animals. Shortly before the onset of metamorphic climax, there is a brief ''deaf'' period during which no auditory acti vity can be evoked from the midbrain, and a loss of connectivity is ob served between medullary and midbrain auditory nuclei. During the fina l stages of metamorphic development, auditory function and neural conn ectivity are restored. The acoustic communication system of the adult frog emerges from these periods of anatomical and physiological plasti city during metamorphosis.